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Commons Digester example source code file (FactoryCreateRule.java)

This example Commons Digester source code file (FactoryCreateRule.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Digester tags/keywords

class, deprecated, deprecated, exception, factorycreaterule, factorycreaterule, new, object, objectcreationfactory, objectcreationfactory, override, sax, string, string, stringbuffer, util

The Commons Digester FactoryCreateRule.java source code

/* $Id: FactoryCreateRule.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.commons.digester;

import java.util.Stack;

import org.xml.sax.Attributes;


/**
 * <p>Rule implementation that uses an {@link ObjectCreationFactory} to create
 * a new object which it pushes onto the object stack.  When the element is
 * complete, the object will be popped.</p>
 *
 * <p>This rule is intended in situations where the element's attributes are
 * needed before the object can be created.  A common senario is for the
 * ObjectCreationFactory implementation to use the attributes  as parameters
 * in a call to either a factory method or to a non-empty constructor.
 */

public class FactoryCreateRule extends Rule {

    // ----------------------------------------------------------- Fields
    
    /** Should exceptions thrown by the factory be ignored? */
    private boolean ignoreCreateExceptions;
    /** Stock to manage */
    private Stack<Boolean> exceptionIgnoredStack;

    // ----------------------------------------------------------- Constructors


    /**
     * Construct a factory create rule that will use the specified
     * class name to create an {@link ObjectCreationFactory} which will
     * then be used to create an object and push it on the stack.
     *
     * @param digester The associated Digester
     * @param className Java class name of the object creation factory class
     *
     * @deprecated The digester instance is now set in the {@link Digester#addRule} method. 
     * Use {@link #FactoryCreateRule(String className)} instead.
     */
    @Deprecated
    public FactoryCreateRule(Digester digester, String className) {

        this(className);

    }


    /**
     * Construct a factory create rule that will use the specified
     * class to create an {@link ObjectCreationFactory} which will
     * then be used to create an object and push it on the stack.
     *
     * @param digester The associated Digester
     * @param clazz Java class name of the object creation factory class
     *
     * @deprecated The digester instance is now set in the {@link Digester#addRule} method. 
     * Use {@link #FactoryCreateRule(Class clazz)} instead.
     */
    @Deprecated
    public FactoryCreateRule(Digester digester, Class<?> clazz) {

        this(clazz);

    }


    /**
     * Construct a factory create rule that will use the specified
     * class name (possibly overridden by the specified attribute if present)
     * to create an {@link ObjectCreationFactory}, which will then be used
     * to instantiate an object instance and push it onto the stack.
     *
     * @param digester The associated Digester
     * @param className Default Java class name of the factory class
     * @param attributeName Attribute name which, if present, contains an
     *  override of the class name of the object creation factory to create.
     *
     * @deprecated The digester instance is now set in the {@link Digester#addRule} method. 
     * Use {@link #FactoryCreateRule(String className, String attributeName)} instead.
     */
    @Deprecated
    public FactoryCreateRule(Digester digester,
                             String className, String attributeName) {

        this(className, attributeName);

    }


    /**
     * Construct a factory create rule that will use the specified
     * class (possibly overridden by the specified attribute if present)
     * to create an {@link ObjectCreationFactory}, which will then be used
     * to instantiate an object instance and push it onto the stack.
     *
     * @param digester The associated Digester
     * @param clazz Default Java class name of the factory class
     * @param attributeName Attribute name which, if present, contains an
     *  override of the class name of the object creation factory to create.
     *
     * @deprecated The digester instance is now set in the {@link Digester#addRule} method. 
     * Use {@link #FactoryCreateRule(Class clazz, String attributeName)} instead.
     */
    @Deprecated
    public FactoryCreateRule(Digester digester,
                             Class<?> clazz, String attributeName) {

        this(clazz, attributeName);

    }


    /**
     * Construct a factory create rule using the given, already instantiated,
     * {@link ObjectCreationFactory}.
     *
     * @param digester The associated Digester
     * @param creationFactory called on to create the object.
     *
     * @deprecated The digester instance is now set in the {@link Digester#addRule} method. 
     * Use {@link #FactoryCreateRule(ObjectCreationFactory creationFactory)} instead.
     */
    @Deprecated
    public FactoryCreateRule(Digester digester,
                             ObjectCreationFactory creationFactory) {

        this(creationFactory);

    }    

    /**
     * <p>Construct a factory create rule that will use the specified
     * class name to create an {@link ObjectCreationFactory} which will
     * then be used to create an object and push it on the stack.</p>
     *
     * <p>Exceptions thrown during the object creation process will be propagated.

* * @param className Java class name of the object creation factory class */ public FactoryCreateRule(String className) { this(className, false); } /** * <p>Construct a factory create rule that will use the specified * class to create an {@link ObjectCreationFactory} which will * then be used to create an object and push it on the stack.</p> * * <p>Exceptions thrown during the object creation process will be propagated.

* * @param clazz Java class name of the object creation factory class */ public FactoryCreateRule(Class<?> clazz) { this(clazz, false); } /** * <p>Construct a factory create rule that will use the specified * class name (possibly overridden by the specified attribute if present) * to create an {@link ObjectCreationFactory}, which will then be used * to instantiate an object instance and push it onto the stack.</p> * * <p>Exceptions thrown during the object creation process will be propagated.

* * @param className Default Java class name of the factory class * @param attributeName Attribute name which, if present, contains an * override of the class name of the object creation factory to create. */ public FactoryCreateRule(String className, String attributeName) { this(className, attributeName, false); } /** * <p>Construct a factory create rule that will use the specified * class (possibly overridden by the specified attribute if present) * to create an {@link ObjectCreationFactory}, which will then be used * to instantiate an object instance and push it onto the stack.</p> * * <p>Exceptions thrown during the object creation process will be propagated.

* * @param clazz Default Java class name of the factory class * @param attributeName Attribute name which, if present, contains an * override of the class name of the object creation factory to create. */ public FactoryCreateRule(Class<?> clazz, String attributeName) { this(clazz, attributeName, false); } /** * <p>Construct a factory create rule using the given, already instantiated, * {@link ObjectCreationFactory}.</p> * * <p>Exceptions thrown during the object creation process will be propagated.

* * @param creationFactory called on to create the object. */ public FactoryCreateRule(ObjectCreationFactory creationFactory) { this(creationFactory, false); } /** * Construct a factory create rule that will use the specified * class name to create an {@link ObjectCreationFactory} which will * then be used to create an object and push it on the stack. * * @param className Java class name of the object creation factory class * @param ignoreCreateExceptions if true, exceptions thrown by the object * creation factory * will be ignored. */ public FactoryCreateRule(String className, boolean ignoreCreateExceptions) { this(className, null, ignoreCreateExceptions); } /** * Construct a factory create rule that will use the specified * class to create an {@link ObjectCreationFactory} which will * then be used to create an object and push it on the stack. * * @param clazz Java class name of the object creation factory class * @param ignoreCreateExceptions if true, exceptions thrown by the * object creation factory * will be ignored. */ public FactoryCreateRule(Class<?> clazz, boolean ignoreCreateExceptions) { this(clazz, null, ignoreCreateExceptions); } /** * Construct a factory create rule that will use the specified * class name (possibly overridden by the specified attribute if present) * to create an {@link ObjectCreationFactory}, which will then be used * to instantiate an object instance and push it onto the stack. * * @param className Default Java class name of the factory class * @param attributeName Attribute name which, if present, contains an * override of the class name of the object creation factory to create. * @param ignoreCreateExceptions if true, exceptions thrown by the object * creation factory will be ignored. */ public FactoryCreateRule( String className, String attributeName, boolean ignoreCreateExceptions) { this.className = className; this.attributeName = attributeName; this.ignoreCreateExceptions = ignoreCreateExceptions; } /** * Construct a factory create rule that will use the specified * class (possibly overridden by the specified attribute if present) * to create an {@link ObjectCreationFactory}, which will then be used * to instantiate an object instance and push it onto the stack. * * @param clazz Default Java class name of the factory class * @param attributeName Attribute name which, if present, contains an * override of the class name of the object creation factory to create. * @param ignoreCreateExceptions if true, exceptions thrown by the object * creation factory will be ignored. */ public FactoryCreateRule( Class<?> clazz, String attributeName, boolean ignoreCreateExceptions) { this(clazz.getName(), attributeName, ignoreCreateExceptions); } /** * Construct a factory create rule using the given, already instantiated, * {@link ObjectCreationFactory}. * * @param creationFactory called on to create the object. * @param ignoreCreateExceptions if true, exceptions thrown by the object * creation factory will be ignored. */ public FactoryCreateRule( ObjectCreationFactory creationFactory, boolean ignoreCreateExceptions) { this.creationFactory = creationFactory; this.ignoreCreateExceptions = ignoreCreateExceptions; } // ----------------------------------------------------- Instance Variables /** * The attribute containing an override class name if it is present. */ protected String attributeName = null; /** * The Java class name of the ObjectCreationFactory to be created. * This class must have a no-arguments constructor. */ protected String className = null; /** * The object creation factory we will use to instantiate objects * as required based on the attributes specified in the matched XML * element. */ protected ObjectCreationFactory creationFactory = null; // --------------------------------------------------------- Public Methods /** * Process the beginning of this element. * * @param attributes The attribute list of this element */ @Override public void begin(String namespace, String name, Attributes attributes) throws Exception { if (ignoreCreateExceptions) { if (exceptionIgnoredStack == null) { exceptionIgnoredStack = new Stack<Boolean>(); } try { Object instance = getFactory(attributes).createObject(attributes); if (digester.log.isDebugEnabled()) { digester.log.debug("[FactoryCreateRule]{" + digester.match + "} New " + (instance == null ? "null object" : instance.getClass().getName())); } digester.push(instance); exceptionIgnoredStack.push(Boolean.FALSE); } catch (Exception e) { // log message and error if (digester.log.isInfoEnabled()) { digester.log.info("[FactoryCreateRule] Create exception ignored: " + ((e.getMessage() == null) ? e.getClass().getName() : e.getMessage())); if (digester.log.isDebugEnabled()) { digester.log.debug("[FactoryCreateRule] Ignored exception:", e); } } exceptionIgnoredStack.push(Boolean.TRUE); } } else { Object instance = getFactory(attributes).createObject(attributes); if (digester.log.isDebugEnabled()) { digester.log.debug("[FactoryCreateRule]{" + digester.match + "} New " + (instance == null ? "null object" : instance.getClass().getName())); } digester.push(instance); } } /** * Process the end of this element. */ @Override public void end(String namespace, String name) throws Exception { // check if object was created // this only happens if an exception was thrown and we're ignoring them if ( ignoreCreateExceptions && exceptionIgnoredStack != null && !(exceptionIgnoredStack.empty())) { if (exceptionIgnoredStack.pop().booleanValue()) { // creation exception was ignored // nothing was put onto the stack if (digester.log.isTraceEnabled()) { digester.log.trace("[FactoryCreateRule] No creation so no push so no pop"); } return; } } Object top = digester.pop(); if (digester.log.isDebugEnabled()) { digester.log.debug("[FactoryCreateRule]{" + digester.match + "} Pop " + top.getClass().getName()); } } /** * Clean up after parsing is complete. */ @Override public void finish() throws Exception { if (attributeName != null) { creationFactory = null; } } /** * Render a printable version of this Rule. */ @Override public String toString() { StringBuffer sb = new StringBuffer("FactoryCreateRule["); sb.append("className="); sb.append(className); sb.append(", attributeName="); sb.append(attributeName); if (creationFactory != null) { sb.append(", creationFactory="); sb.append(creationFactory); } sb.append("]"); return (sb.toString()); } // ------------------------------------------------------ Protected Methods /** * Return an instance of our associated object creation factory, * creating one if necessary. * * @param attributes Attributes passed to our factory creation element * * @exception Exception if any error occurs */ protected ObjectCreationFactory getFactory(Attributes attributes) throws Exception { if (creationFactory == null) { String realClassName = className; if (attributeName != null) { String value = attributes.getValue(attributeName); if (value != null) { realClassName = value; } } if (digester.log.isDebugEnabled()) { digester.log.debug("[FactoryCreateRule]{" + digester.match + "} New factory " + realClassName); } Class<?> clazz = digester.getClassLoader().loadClass(realClassName); creationFactory = (ObjectCreationFactory) clazz.newInstance(); creationFactory.setDigester(digester); } return (creationFactory); } }

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